Cummins 350 HP ISL Engine with Allison 3000 MH 6. The control panel has the MODE button...but I've not used it or changed any setting from that of the factory. We put 20,000 on the Diplomat with the cruise control working fine. Then the 6th-to-5th shifting (when initiating the cruise control) became intermittent. It seemed that stopping and turning-off the engine (like: at a rest stop) would "reset" something, and the cruise control would work fine for a while. But here of late, the 6th-to-5th shift happens all the time when turning the CC on.